Combination fan and limit switch structure



y 1939- B. E. SHAW 2,158,437

COMBINATION FAN AND LIMIT SWITCH STRUCTURE Filed Feb. 21, 1938 Patented May 16, 1939 UNITED STATES COMBINATION FAN AND LIMIT SWITCH STRUCTURE Burton E. Shaw, Bristol, Ind., assignor to Penn Electric Switch 00., Goshen, Ind., a corporation of Iowa Application February 21, 1938, Serial No. 191,646

10 Claims.

An object of my invention is to provide a combined fan and limit switch structure which is Simple and has inexpensive and readily operable means for changing the differential of operation of 'the fan switch, and changing both the range and the differential of operation of the limit switch.

A further object is to provide a combined fan and limit switch having a thermostatic element the like and toprovid-e a pair of switch units, both operable from the same thermostatic element so that the fan switch may be controlled at one temperature and the limit switch at another tem perature as desired, -means being provided in the form of pointersand a scale to permit resetting of the switches for different temperature operations and for indicating the temperature setting thereof as desired] A further object is to provide switches which are operated from a rotatable rod and which can be adjusted as to their differential of operation and range of operation by the setting of switch actuating arms relative to a graduated disc on which the temperature corresponding to different positions of rotation of the rod is calibrated.

Still a further object is to provide in connection with a switch, means to operate the switch including a cam and means to widen the differential of operation of the switch including a pair of stop arms which can be varied as to spacing between them and which engage opposite sides of a projection from a camas the stop arms are rotated in different directions by a thermostatic element or other condition responsive means.

Another object is to provide means for changing the range of operation of a second switch cam by means of a switch actuating arm adjustable in a manner similar to the stop arms, all three of the arms being locked in the desired position/relative to a thermostatically operated rod or the like by a single lock nut.

Another object is to provide a means for chang ing the differential of operation of a switch and consisting of two cams, one of which is steeper than the other cam, the cams being rotatable relative to each other so that the cut in point and the cut out point of the switch can be determined by either cam or the cut in point can by the other cam.

Still another object is to provide a switch and a cam for operating it, thecam being so constructed that it can operate an actuating arm in such manner that the cam can rotate further mounted in a plenum chamber of a furnace or be determined by one cam and the cut out point 7 than one revolution without the lobe of the cam engaging the arm and actuating the switch twice during such rotation.

With these and other objects in view, my invention consists in the described construction, arrangement and combination of the parts thereof whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawing, in which:

Figure 1 is a front elevation of a combined fan and limit switch structure embodying my present invention with a part of the cover I broken away and the switch shown at substantially room temperature.

Figure 2 is a view of parts of Figure 1 with one of the switch casings shown in section and with the graduated disc removed so that the cams which actuate the switches can be illustrated.

' Figure 3 is an enlarged sectional view on the line 33 of Figure 1.

Figure 4. is a sectional view on the line l-l of Figure 3 showing the cam mechanism for the limit switch of my structure.

Figures 5 and 6 are viewsv similar to a portion of Figure 2 showing the fan switch operating cam, in different positions; and

Figure 7 is a sectional view on the line '|'l of Figure 3.

On the accompanying drawing I have used the reference numeral ID to indicate generally a switch housing and 12 the cover thereof. The back of the switch housing is indicated at I3. Extending through the back" I 3 is an actuating rod 14 which is rotated in response to temperature changes by a coiled bi-metallic element l5. One end of the element 15 is secured as at Hi to the rod I 4 while its other end is secured as at I! to a stationary hub 18 which is supported on the back l3 in any suitable manner.

Loosely mounted on the outer end of the-rod H is a sleeve l9 and rotatable on the sleeve I9 is a second sleeve 20. A cam C is riveted to one end of the sleeve 20. A second cam C is rotatable on a shouldered portion at one end of the sleeve l9 and a third cam C is riveted to said end of the sleeve.

Secured to the operating rod H is a third sleeve 2|. The outer end of the rod I4 is split whereit extends into the sleeve 2| and is held in an expanded condition by a screw 22 so that the rod frictionally engages the bore of the sleeve as fully described in my co-pending application, Serial No. 179,706, filed December 14, 1937.

Slidable and non-rotatable on the sleeve 2| lid is an indicator disc D. The chsc D as shown in myco-pending application has a bore which fits flat sides 23 of the sleeve 2i so as to provide for such sliolable and non-rotatable movement of the disc relative to the sleeve. Between the disc D and a shouldered portion Ella, of the sleeve H, I provide switch actuating arms 26, 25 and 26. These arms are provided with pointers 27!, 28 and 29 respectively for cooperation with indicating scales on the front of adisc D graduated for instance in degrees of temperature as shown in Figure 1. An arrow A is provided on a bracket B for cooperation with the indicia on the disc D. All three of the arms 2 25 and 26 are normally locked against rotation relative to the sleeve 2i and thereby relative to the rod M! by a lock nut 3U. This lock nut may be loosened andthe pointers 2t, 28 and 29 adjusted relative to the scales on the disc D as desired and as will hereinafter appear.

vided with stops 3i and 32. The cam C is provided with a projection such as a lug 33 extending to a position between the stops 3i and 32. The stops 3i and 32 are adapted to engage opposite sides of the projection 33 as illustrated in Figures 5 and 6 as the rod I4 and thereby the switch actuating arms 24 and 25 are oscillated in opposite directions.

The cams C and C" are normally retained in a predetermined position relative to each other by a lock screw Si l extending through a slot 3511 (see Figures 3 and 4). These cams are operated from the rod M by the switch actuating arm 26 which has a projection 35 extending inwardly from its rear surface, The projection 35 enters a notch 36 movable contact 46.

of an arm ill, The arm 37] is riveted tothe end or the sleeve l 9 opposite the cams C and C".

The back of the disc D is provided with serrawhich they might be adjusted relative to the disc D. a

The bracket B is supported in the housing id and in turn supports a pivot pin ii. Actuating arms t2 and d3 are pivoted on the pin it and engage the cams C, C and C. The actuating arm controls a limit switch LS while the actuating arm d3 controls a fan switch FS. These switches are in the form of units, one of which has been shown partly in section in Figure 2. Briefly each unit includes a switch arm Ms pivoted as on knife edges 5 and operatively connected with a A stationary contact is shown at dl. At 48 an armature isillustrated and at M] a permanent magnet is shown for cooperation with the armature to provide for snap action of the switch. lihe contacts may be separated by pressing inwardly on a pin 50 until the tension of a spring 513a overcomes the magnetic pull and thereby the armature is released so that the switch arm can snap to a position separating the contact it from the contact'l.

Practical operation perature assume substantially the position shown in Figure l. The limit switch LS is on and the fan switch FS is ofi. As the temperature in the plenum chamber of the furnace increases,

for instance to one hundred degrees, the switch The switch actuating arms 24 and 25 are pro-- amen-av actuating arms 2d and 25 will swing to approximately the position in Figure 2. Finally the stop 32 will catch up with the projection as in Figure 5 when the temperature has risen to about one hundred fifty degrees.

It will be noted that the cam C has a lobe 5i and adjacent the top of the lobe there is a notch 52. This notch is provided so that when it registers with the actuating arm it, the cam will be held in that position until the stop 32 can catch up with the projection By way of example, the friction between the parts may be such that the cam will remain in the same relative position to the arms 2iand 25 as shown in Figure 2 while moving from the position in Figure 2 to the position in Figure 5. Accordingly as soon as the notch 52 registers with the actuating arm 43, the spring 5lia of the fan switch FS will serve to retain the cam C in position until the stop 32 catches up with the projection 33 instead of the cam being rotated on to the position of Figure 6. Upon reaching the temperature for which the pointer 28 is set, as in Figure 6 (one hundred seventy-five degrees), the energy stored in the bi-metal element l5 will cause the notch 52 to pass the actuating arm 43 and the arm will quickly swing to on position for the fan switch PS, the cam C rotating on to the position shown in Figure 6 due to the momentum imparted thereto by the actuating arm 43 traveling along the lobe 5B. Thus the notch 52 insures that the differential of operation of the fan switch FS will be as wide as determined by the actuating arms 24 and 25.

In the return direction, when a temperature of one hundred twenty-five degrees is reached (according to the setting shown in Figure l) the stop Si of the actuating arm M will have moved the projection and thereby the cam C to a position so that the lobe bl will move the actuating arm. 43 to its switch opening position.

Under certain excess temperature conditions, the cam C will rotate further than one revolution. In order that the switch FS is not operated a second time by the lobe M, I have provided a projection 53 on the cam which has an outer surface coincident with the high portion of the cam and an arcuate notch 5d coincident with the low portion of the cam which two portions are separated by the lobe 50. I The notch Fi l receives the upper end of the actuating arm ii; when more than one revolution of the cam occurs. Likewise the cam C is provided with a similar projection and an arcuate notch M for the same reason. When the bi-metallic element i5 is heated to a temperature of two hundred degrees, the cams C and C" will operate to open the limit switch LS.

In connection with the switch units LS and PS, the spring 5ila provides for a diiferential of operation of the switch due to the necessity of this spring being compressed during the switch opening operation and expanded during the switch closing operation when bucking the pull of the magnet on the armature and permitting the magnet to pull the armature to closed position respectively. This differential of operation is translated in movement of the actuating arms 12 and to positions indicated by dotted lines a and b, which indicate the switch opening position and the switch closing position respectively of the switch units. Accordingly in Figure 4, the cam C has just rotated counterclockwise to switch closing position. In rotating clockwise, the cam C will engage the actuating arm til and deter mine the switch opening position when the point where the line crosses the lobe of the cam C" and registers with the switch actuating-arm. It is obvious that as the cam C" is rotated counterclockwise relative to the cam C after loosening the screw a the differential of operation will be increased while adjustment in the opposite direction will cause narrowing of the differential of operation.

The construction disclosed makes it possible in a switch structure to secure variation of the difierential as well as variation in the range of operation of the switch units in a very convenient manner. The scales on the disc D provide determination of the range of both switchesand the differential of operation of the fan switch. The differential of operation of the limit switch may be varied by relative adjustments of the cam C and C which are preferably set at'the factory since theadjustments indicated on the disc D are the only ones requiring change after installation in a particular job.

Some changes may be made in the construction and arrangementof the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim as my invention:

1. In a combination fan and limit switch structure, a fan switch, a limit switch, a rotatable rod for actuating said switches, a temperature responsive element-operatively connected with said rod for rotating it in response to changes of temperature in a plenum chamber or the like and means for actuating said switches from said rod comprising a cam coacting with said fan switch, said cam being rotatable relative to said rod, a disc fixed to said rod, a pair of stops movable circumferen ially relative to said disc, means for locking aid stops relative to said disc, said cam having means projecting between said stops whereby said cam is rotated in one direction by one of said stops and in an opposite direction by the other of said stops, the distance between said stops determining the width of differential of operation of said fan switch, a second cam rotatable on said rod, means for locking said second cam relative -to said disc, said second cam coacting with said limit switch to operate it through a predetermined. range and means to effect a change in differential of operation of said limit switch comprising a third cam cooperating with said second cam to change the relativev effective cut in and'cut out points of said second cam.

2. In 'a combination fan and limit switch structure, a fan switch, a limit switch, temperature means for actuating said switches including a cam coacting with said fan switch, said cam being movable relative to said temperature responsive means, a pair of stops movable relative to said temperature responsive means, a lock for said stops relative to said means, said cam having a projection between said stops whereby said cam is moved in one direction by one of said stops and in an opposite direction by the other of said stops, the distance between said stops detercam and effective to determine the relative cut in and cut out points thereof.

3. In a switch structure of the characterdescribed, a switch unit, a rotatable rod for actuating said switch unit, a condition responsive element operatively connected with said rod for rotating it in response to condition changes and means for actuating said switch unit from said rod comprising a cam coacting with the switch unit to operate it through a given range and means to effect a change in differential of operation of said switch unit comprising a second cam cooperating with said first cam to change the effective cut in point of said first cam relative to the cut out point thereof. 7

4. In a switch of the character described, a rotatable actuating element, a disc non-rotatable relative thereto, a pair of switch actuating arms rotatable on said actuating element, a third switch actuating arm rotatable on said actuating element, means for locking said disc and allthree of said arms on said actuating element against rotation relative'thereto with said first two arms spaced' from each other, a switch, a switch actuating element therefor and located between said first two arms for alternate actuation by said two arms as they move in oppo-. site directions, the distance between said two arms determining the differential of operation of said switch, a second switch and a second switch actuating element therefor and operatively connected with said third arm.

5. In a switch structure, an actuating element, three switch actuating arms rotatable thereon, means for locking said arms on said actuating element against rotation relative thereto with said two of said arms spaced from each other, a switch, a switch actuating element therefor and located between said two arms for alternate actuation thereby as they move in opposite directions, the distance between said two arms determining the differential of operation of said switch, a second switch and a second switch actuating element therefor and operably connected with the third arm.

6. In a control switch, a rod, condition responsive means for rotating said rod, a pair of arms rotatable on said rod, a third arm rotatable on said rod, means for locking said arms relative to said rod with the first two arms spaced from each other, a cam rotatable on said rod and having a projection extending to a position between said first two spaced arms, a switch actuated by said cam, a second cam rotatable on said rod and operatively connected with said third arm and a secondswitch actuated by sai second cam.

-'7. In a control switch, a rod, condition responsive means for rotating said rod, a pair of arms rotatable on said rod, a third arm rotatable on said rod, means for locking said arms-relative to said rod with the first two arms spaced from each other, a cam rotatable on said rod and having a projection extending to a position between said first two spaced arms, a switch actuated by said cam, said switch including means resiliently engaging said cam and a notch in said cam adjacent the lobe thereof for retaining said cam against rotation when one of said first two arms is spaced from said projection and is moving toward it and until said arm engages said projection and effects movement of it to thereby move the cam to a position beyond said means resiliently engaging the cam, a second cam rotatable on said rod and operativelyconnected with said third arm and a second switch actuated by said second cam.

8. In a control switch, a rod, condition responsive means for rotating said rod, a cam on said rod, a control switch for actuation by said cam and having actuating means coacting therewith to effect such actuation, said cam having a high portion, a low portion and a lobe separating said portions and means to permit more than one revolution of said cam without-operating said control switch twice comprising a circumferentially arranged projection having a surface coincident with said high portion and overhanging said low portion, the space between said projection and said 10w portion receiving said actuating means after said lobe passed the actuating means and coacts with said low portion and the cam continues to rotate.

9. In a control switch, a rod, condition responsive means for rotating said rod, a cam on said rod, a control switch for actuation by said cam and having actuating means coacting therewith to effect such actuation, said cam having a high portion, a low portion, a lobe separating said portions and a circumferential projection ha antenna has a surface coincident with said high portion and overhanging said low portion, the space between said projection and said low portion permitting reception of said actuating means.

10. in a combination fan and limit switch structure, a fan switch, a limit switch, a rotatable rod for actuating said switches, a temperature responsive element operatively connected with said rod for rotating it in response to changes of temperature in a plenum chamber or the like and means for actuating said switches from said rod comprising a cam coacting through a lost motion connection with said fan switch, the degree of lost motion in said lost motion connection being variable and determining the width of differential of operation of said fan switch, a second cam on said rod coacting with said limit switch to operate it through a predetermined range and means to effect a change in the differential of operation of said limit switch comprising a third cam cooperating with said second cam to change the relative eifective cutin and cut-out points of said second cam.

BURTON E. SHAW. 

